Catching a ‘silent’ cow killer: A simpler detection system to help dairy farmers stay ahead of a costly disease

By David Tenenbaum, UW-Madison University Communications

February 13, 2018

Mitch Breunig BS’92 has been around dairy cows long enough — all his life, to be exact — to suspect something was amiss with two of his Holsteins.

And he’s been around the Department of Dairy Science long enough — considering he’s an alumnus and his 450-cow farm in Roxbury, Wisconsin, is practically a field research station for the department — to suspect ketosis.

This “silent killer” is caused by excessive toxic particles released by the liver, usually when a cow starts to produce milk after giving birth. So it was fortuitous that Heather White, an assistant professor of dairy science and one of the world’s experts on detecting ketosis, was visiting Breunig’s Mystic Valley Dairy, within sight of the St. Norbert’s church steeple in northwestern Dane County, on that day in March.

Heather White (left), assistant professor of dairy science, talks with dairy farm owner and UW alumnus Mitch Breunig (right) at his farm in Roxbury, Wisconsin. White and her students are looking for ways to detect ketosis in dairy cows. Photo: Bryce Richter

The start of lactation is the moment of maximum metabolic stress for a dairy cow, when her overworked liver can crank out molecules called ketones that provide energy to other tissues in the body. But if ketones reach excessive levels, they can reduce milk output, set the stage for disease, and even cause the cow to be culled from the herd.

Milk output from the cows in question had dropped, which could have had many causes. Ketosis, however, appears in 40 to 60 percent of lactating American dairy cows.

Even though ketosis costs farmers an average of $290 per cow, it’s often undiagnosed because the blood tests are laborious and expensive. Far better would be a test for telltale molecules in the milk, which is exactly what White has been working on, in collaboration with dairy science department chair Kent Weigel MS’92 PhD’92 and Gary Oetzel, a professor of medical sciences at the UW–Madison School of Veterinary Medicine.

The result of their labor, called KetoMonitor, is now incorporated in the AgSource system used by dairy farmers across the state to track their herds and milk output. AgSource relies on a sophisticated spectrometer to look for two milk-borne compounds that signal ketosis and then refines the prediction through an advanced computer analysis.

When Ryan Pralle BS’15 and Rafael Caputo Oliveira, both graduate students who work with White, sampled blood from the two cows, Breunig’s hunch proved correct. The cows had a silent, or “subclinical,” ketosis. Armed with that knowledge, Breunig began corrective measures that usually tame ketosis, such as dietary supplements.

Blood tests are the old-fashioned but still gold standard method for detecting ketosis. But KetoMonitor’s milk tests and computation have become the first line of defense.

By testing milk from “fresh” cows every week or so, KetoMonitor first estimates the prevalence of ketosis in the fresh cows. Then, by analyzing the data on milk production, reproductive history, and other matters on each fresh cow, it identifies cows that might need a blood test for ketosis.

The result of a blood sample test used to detect ketosis in dairy cows is displayed. Photo: Bryce Richter

KetoMonitor already catches 85 percent of cows with the condition, which is almost enough to avoid blood tests entirely. Once they reach 90 percent accuracy, blood tests for every fresh cow would no longer make economic sense, White says.

To reach that magic number, Pralle is using a computational tactic called “machine learning” (think digital self-help class). When the software makes a mistake, it combs through the data, looking to do better next time around. The accuracy is improving, he says. “When we compare it to some other non-blood tests, I think our tools are very competitive.”

White and her collaborators began tackling the problem about 10 years ago. “We recognized there is a lot of money lost in subclinical ketosis,” she says. “A cow is having negative outcomes — she’s making less milk and is not going to rebreed as easily, but she can’t walk up and tell you she’s sick.”

Due to the efforts of White and others at UW– Madison and beyond, that has changed. “Ketosis has become something that producers really want to manage because they recognize the cost of the disorder,” says Pralle.

None of this is lost on Breunig, who sees a future with more constraints as a prime reason to focus on efficiency. “We will be in a position where we will need to grow more food on less land with fewer cows.”

KetoMonitor can help in unexpected ways, Breunig says. “When we adapted to the market by eliminating BST [the hormone bovine somatotropin], we had to change nutrition and management, and we used KetoMonitor to assess the impact of those changes.”

“Advances like KetoMonitor help us keep the herd healthy and allow us to stay competitive,” he says. “That’s the kind of help we really need.”